The invention relates generally to in-tank fuel filters and more specifically to an in-tank fuel filter having layers of spun bonded and melt blown filtration media and an outer shell of extruded mesh.
The modular assembly approach to motor vehicle manufacture increasingly demanded and practiced by automobile manufacturers has effected the design and componentry of motor vehicles in numerous ways. With regard to fuel systems, and particularly the fuel supply and filtration components, fuel filters have changed from a single, in-line assembly typically disposed under the hood and adjacent the carburetor, such as disclosed in U.S. Pat. No. 4,036,758, to modular designs wherein a filter, fuel pump and fuel level sensor constitute an assembly which is disposed within and secured to the fuel tank. Such an in-tank filter is described in U.S. Pat. No. 4,961,850.
Typically, such in-tank filters comprise a single layer of a woven nylon, polyester or acetal fabric which is folded and sealed by heat, radio frequency or ultrasonic energy along its edges. In order to improve small particulate filtration capability, the exterior woven fabric layer may be supplemented by an interior non-woven layer having finer pores which provide improved small particulate filtration capability. Given the comparative pore sizes of the outer and inner layers and the particulate filtration capability required of such filters, the exterior layer, in fact, provides little from the standpoint of filtration. Rather, it is present primarily to provide a suitably durable protective covering for the non-woven interior layers.
Such protection is also necessary because such in-tank filters are disposed either on the end of a suction tube or directly at the inlet of an in-tank fuel pump. In order to achieve the maximum withdrawal of fuel from the tank, the filter is positioned, and in some installations pressed, against the bottom surface of the fuel tank. In this condition, the lower surface of the fuel filter is subjected to abrasive action due to the small though inevitable relative movement between the filter and the bottom surface of the fuel tank.
The present invention addresses problems associated with this type of filter installation, achieves the small particulate filtration capability of melt blown filtration media and exhibits excellent abrasion resistance due to the incorporation of an extruded mesh outer shell.